It is generally known that, in order to manufacture an absorbent component using an airlaid process, the fibers and fibrous shreds used in the process are produced beforehand by grinding a fibrous material, such as pulp. Notably, natural fibers such as those made from cellulose are manufactured from this type of fibrous web. The grinding and shredding preferably takes place in what are referred to as hammer mills, where the fibrous material is fed onto the transversely aligned cutting edge of a cutting mechanism and wherein several striking elements arranged on a drum strike one end of the fibrous material projecting over the cutting edge.
In forming absorbent components for absorbent articles, it is typical to utilize a fibrous material that is provided in the form of a roll, which allow for a continuous process that can run at relatively high rates of speed. However, a rather limited number of fibrous materials are available in the form of a roll, as compared to fibrous materials provided in individual sheet form, thereby limiting the types of fibrous materials that can be utilized to make absorbent components for absorbent articles.
Although more types of fibrous materials are available in individual sheet form as compared to rolled form, individual sheets of fibrous materials are difficult to utilize in a commercial scale continuous process for making absorbent components, because it is difficult to maintain a constant mass flow as gaps tend to form between the individual sheets as each is conveyed into a hammer mill for grinding.
Devices and methods for grinding and shredding fibrous materials are known, for example, from DE 22 45 819 A1. In the known device, the cutting edge is formed into a casing by a slotted inlet opening which encases a drum body with a plurality of striking elements. In this process, the striking elements are advanced to the inner end of the slot leaving a narrow clearance, such that the incoming fibrous material is ground by the rotating drum body. Devices of this type have the great disadvantage that very irregular fibrous shreds are produced where relatively elastic fibrous materials are used. Due to the elasticity of the fibrous material, the breaks in the fibrous material occur primarily beyond the cutting edge.
In the prior art, therefore, a method and a device are known with which the fibrous material is immobilized by an additional clamping mechanism in the region of the cutting edge. The known method and the known device are described in EP 0 386 017 B1. Here, the fibrous material is fed to the cutting edge of the cutting mechanism. A clamping mechanism is arranged at a short distance from the cutting mechanism, which features two opposing clamping jaws that grip on the lower surface and the upper surface of the fibrous material. One of the clamping jaws is designed to be moveable and this results in the fibrous material being clamped in an oscillating manner. Hence, this lends additional stability to the fibrous material during grinding.
The known methods and devices, however, have a great disadvantage insofar as the point in time at which the fibrous material is clamped and the point in time at which the fibrous material is ground must be synchronized with each other in order to obtain fibrous shreds in defined sizes and maintain a constant mass flow in a continuous process. Furthermore, it is impossible with the known method and device to produce very fine fibrous shreds because of the interval as designed between the cutting mechanism and the clamping mechanism.
There thus remains a need to provide an improved process for making absorbent components, especially utilizing individual sheets of fibrous materials to make the absorbent components in a continuous process.